


Swinging By

by Ravvi



Category: Undertale (Video Game)
Genre: Aftercare, Begging, Bondage, Consensual, Ecto-Genitalia (Undertale), Knifeplay, Other, Penetration, Sex Swing, Swapfell Sans, Underfell Sans, blackcherry, dom/sub elements, pain-play
Language: English
Status: Completed
Published: 2017-09-15
Updated: 2017-09-15
Packaged: 2018-12-30 01:19:21
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 2,526
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/12097566
Author URL: https://archiveofourown.org/users/Ravvi/pseuds/Ravvi
Summary: Who put this random, smutty scenario in my imagination?  And why does it have knives???Sketch to help with body positions and such here: https://ravvi-k.tumblr.com/post/165392014908/swinging-by-sketch





	Swinging By

Edge had always told him he should pay more attention to his surroundings.  Red irritably reflected that this advice was, in fact, useless.  Apart from the tickle of a near-invisible string breaking against his tibia, there had been no warning before he’d become hopelessly ensnared in what he could only imagine was one of his brother’s newest traps.

 “God damn it,” Red sighed, looking down at the cat’s cradle of silk thread wrapped snugly around his body.  The trap had caught him mid-step, so he was partially suspended with one foot in the air and his arms pinned at his sides.  An awkward sideways hop only knocked his remaining foot out from under him, making the strings snap taut and leaving him hanging in the middle of the path with his knees slightly bent and toes just brushing the snowy ground. 

“What the fuck kind of trap is this?” he muttered, eyelights tracing the white, shimmery thread until it disappeared against the snow.  Judging by the way the trees around him were bent, he was tied off to four pines with trunks that were bigger around than he was tall, and with so many strings that his torso and legs looked like they'd been encased in a gossamer net.  It was actually kind of impressive.... 

Too impressive, actually.  Edge wasn’t the dumbest monster in the underground, but there was no way he’d pulled something _this_ sophisticated out of his ass.  His brother’s traps were straight-forward and obvious, designed to intimidate and discourage.  Not only had this trap actually succeeded in capturing him, it had done so in complete silence, and with unnerving efficiency. 

And that meant…

“You’ve got one hell of a way of saying hello,” Red called out to the empty forest with a broad grin.  “I’d offer to shake your hand, but I’m a little-“

“Don’t you DARE finish that-“

“Tied up at the moment?”

“OH MY GOD,” Black scowled, walking out of the trees and up to his captive with a loose, predatory stride.  “I spent FOUR HOURS setting this trap, and that’s the best you can come up with?”

Red grinned at him silently, suppressing a bout of giggles as his interdimensional double’ scowl darkened.

“Well?  Is it?!” Black finally snapped.

“Sorry, I’m a little tongue-tied.”

“Oh ARE you now?” Black growled over his captive’s snickers.  “I sincerely doubt it.  Your mouth is the one thing you aren’t lazy about using, mutt.”

Red snorted loudly.  “I know three monsters off of the top of my head who’d DEFINITELY say otherwise,” he said, bringing his sharpened teeth together with a quiet _snick_.

“They simply didn’t know how to motivate you properly,” Black said dismissively, prowling slowly around Red’s dangling body.  His expression softened to a smirk as he drank in the sight of the other skeleton.  The trap had forced his shirt and jacket to ride up, revealing several of his larger vertebrae and floating ribs.  The smooth, ivory bones were delightfully vulnerable-looking against the backdrop of snow and shimmery, silk thread. 

“Though of course, it does help to have a lot of… _leverage_ ,” Black purred, giving Red’s backside a gentle push.  Red jerked a little, shoulders hunching and hands reflexively pulling outward against their restraints as he swung back and forth.  “The original design used steel piano wires instead of spider-silk, you know.  The result was a lot more…terminal.”

“Charming,” Red commented affably, letting his toes make little furrows in the snow as he swung back and forth.  “I like this one better.”

“You know, it’s growing on me too,” Black mused, running his fingers lightly along a strand that was tangled around Red’s legs.  “There is a certain elegance to capturing someone…”

He tugged on the strand, hard enough to make Red stop swinging with an abrupt jerk.

“…alive.”

“Dawww.  Look at Edgy McEdgelord, going soft as a kitten,” Red grinned, voice disappointingly even.  “Soon you won’t even sound like a b-rated horror villain every time you ask Slim to pass you the goddamn Cheerios.”

“Soft?” Black scoffed, summoning a slender, edged bone between his fingers.  “I sincerely hope not.  I would be badly disappointed if the sight of you so thoroughly ensnared by my handiwork ever wore thin.  It looks so good on you…”

Red jumped, then relaxed with a little sigh as Black cupped his head and pressed a light kiss against the underside of his jawbone. 

“And it makes the trip so, very worth it…”

Another kiss, this time with the light scrape of teeth against his cervical vertebrae.

“And it would be such a shame to waste this opportunity…”

“Hnmmm?” Red squeaked as Black pressed his head backward and forced his tongue past his teeth.  Red’s tongue immediately sparked to life and pushed against the invasive kiss, toes scrabbling at the snow as he struggled to get some purchase.  Black casually slipped one hand between the other skeleton’s legs, tugged him forward until his feet were dangling a few inches above the ground, and delved deeper into his captive’s mouth.  Red squirmed as the sudden pressure against his pelvic inlet sent a rush of tingles through his legs, gasping around Black’s tongue as he tried to decide whether he actually wanted to resist.

“Still an ill-behaved brat, I see,” Black murmured after a long moment.  “It’s time I finally whipped some manners into you, mutt.”

Motions smooth and feather-light, Black drew the flat of his bone dagger down the side of Red’s face.  Red shivered, cheek tingling and hyperaware of the makeshift knife slipping coldly over the bone.

“Do you want to continue?”

“G-green,” Red stuttered.

“Was that a stammer I heard?  Where are all of your revolting puns and inane comments now?” Black snickered, face flushed dark cyan as he drew the blade down the curve of his captive’s chest, letting the sharpened bone bump lightly over each rib. 

“Not gonna lie, I’ve got a bit of a thing with knives,” Red quavered, eyes still fixed on the makeshift dagger.  He didn’t know why, but he was equal parts fascinated and terrified by knives.  The sight of one in Black’s hands, moving ever-so-delicately over his ribs, was strangely thrilling and made a hard, tingling knot of anticipation form somewhere below his ribs.

“Then you haven’t played with these before?” Black asked, sounding surprised.  Red shook his head.  “I see.  Well then, here’s how this is going to work.  I’m going to cut you.  Every time I do, I want you to say ‘yes’.  Loud and clear.  If you want me to stop, then say ‘blue,’ just like always.  I’ll be watching the whole time in case you get overwhelmed, but I want you to _tell me_ before that happens.  Do you understand?”

“…yes?”

‘”Very well…” Black gently drew the blade along the crest of his captive’s ilium.  Red inhaled sharply, watching the blade with an expression that was somewhere between fascination and dread.  Black grinned, heat and pressure blooming across his pelvic inlet as the sound went right to his groin.

“Such an adorable little mutt.”

He pressed down, making a shallow scratch across the bone.  Red flinched with a little gasp, and the injury began to glow as his body rushed to repair the damage.

“But still so _fucking_ disobedient.  Didn’t I just tell you to be _verbal,_ fucktoy?

“Hnn-“ Red choked as Black repeated the cut on the other side, making the slice a little deeper, and twice as long.  “Y-yes…”

“Not loud enough,” Black breathed, and made another light cut. 

“Yes!  Fuck you-” Red spat.  Black grinned wildly.

“Better, but you’ve got room for improvement,” he breathed, lightly tracing the outline of Red’s vertebrae with the fingers of his free hand.  “Luckily, we have lots and lots of time.  By the end of this, I want you screaming, mutt.” 

Roughly, he ran his fingertips across the scratches.  Red jumped, then trembled as a prickling sting spread across his iliac crests, making his toes curl and hands clench into fists at his sides.

“You getting off on this, you freak?” Red gasped, ilium throbbing as Black pulled away.  “That’s pretty fucked up, even for you.”

“Don’t fool yourself, pet,” Black tutted, drawing the blade once down the back of Red’s spine, then slicing through the back of his shorts in one, quick slice.

“Ah! Y-yes…” Sans yelped as Black flicked the blade against his sacrum, leaving a small cut in the bone.  A single finger rubbed lightly against the damaged spot, sending stinging jolts across his pelvis as heated magic rushed downward and left him wildly unsure whether he was actually in pain.

“Not when I can see you getting so wet for me.  You love my knife, don’t you, you little slut?”

 “YES!” Sans yelled as Black made two, quick cuts on the inside of his left femur.  “FUCK!  I’m YELLING, OK?!  I’m Y-AAHHHH!!  YES!”

“Much better,” Black purred, drawing the knife slowly across his other femur.  Red whimpered, then screamed again as the blade cut through the hard, outer layer of bone with a sharp sting that rapidly faded into a heady throb.  “See, doesn’t that feel better than holding it in?”

“Yes…haahhhh _,_ ” Red gasped, lying limply in the restraints as Black gently thumbed over the new cuts.  For some reason, the pain felt muted, like his nerves were being smothered under a warm, fizzy liquid.  His head was pounding, and his pelvis _ached_ in the best possible way...

“Are you trying to hump my hands?” Black snickered, keeping his motions across the damaged bone slow and rhythmic.  “Oh, _Red._ Are you really getting off on this after you accused _me_ of being fucked up?”

Roughly, he flicked the other skeleton’s pubic symphysis, face glowing as the other skeleton writhed under his hands and a glowing, crimson shaft formed under his fingers.

“You dirty little fucktoy,” Black chuckled, drawing his fingers lightly Red’s length.  “What are you doing, putting this in my hands?  Do you want me to cut this too?”

“N-no!  P-please, not there!” Red gasped. 

“Very well,” Black purred, then dismissed the knife, stepped out of his own pants, and kicked them away.  “Now what to do with you instead?  Perhaps you should start by apologize for insulting me, sluttoy.”

“Haahh, I-I’m s-sorry!” Red gasped as Black ran his fingers once down his captive’s cock, then guided it between his legs and rubbed it slowly over the rim of his pelvic inlet.

“Sorry for what, mutt?” Black breathed, heat and pressure rushing downward as his own magic coalesced into a dark, cyan pussy.

“SORRY FOR INSULTING YOU,” Red howled, hips bucking impotently as Black slowly dragged him forward, spreading blue slick over Red’s rapidly hardening shaft.

“As you should be.  Now, what should I do with this?”  Black asked, teasingly letting Red slip back a few inches before dragging him forward again.

“F-fuck me,” Red choked, legs trembling as beads of marrow slowly dripped down his body.

“Louder, cur.”

“I WANT YOU TO FUCK ME PLEASE!”

“Good boy,” Black grinned, then thrust forward, taking the full length of Red’s cock in a single stroke.  Red moaned, then squirmed with frustration as Black pulled back and bobbed back and forth with shallow, desperately unsatisfying motions.

“What’s the matter?” Black cooed, using the strings of the trap to force his captive back and forth.  “I thought you said you wanted me to fuck you?”

“T-to…fucking slow,” Red groaned, hips bucking impotently as Black kept the pace torturously slow.  “HOLY FUCK, PLEASE-“

“You want to come?  Already?” Black snorted, watching Red’s tortured expression with open delight.

“YES!”

“Too bad.”

“AGHHHHH!” Red screeched as Black continued to ride him, completely helpless to change the pace as he was worked to orgasm with unbearable slowness. 

“What’s this?  You want me to stop?” Black snickered, pulling completely away and leaving Red’s painfully erect cock completely without stimulation.

“NO!  PLEASE LET ME COME M’LORD!” Red screamed.  Black inhaled, expression rapidly dissolving into something darker and more primal as he drove forward with a feral growl.

“Now why would you use that name with me, fucktoy?” he growled, almost sounding angry as he rode his captive so hard that Red immediately arched back with a desperate wail.  "Were you hoping to get me off?  Because guess what?  It worked."

"Puh-p-please, oh _fuck-"_ Red gasped, sweat pouring down his face as Black slammed into him again and again.

“Say it," Black snarled, fingers curled tightly around Red's dripping ilium.  "Say it again, fucktoy.  Scream it when you come.”

“Haahh, haahhh, haahh, M-M’LORD!” Red wailed, hips jerking as Black milked him through the orgasm with slick, powerful strokes that left him arched, and then slumped over in his captor's arms.

“Good boy,” Black panted, pressing loose, messy kisses over Red’s neck and jaw as he slowly came down from the high.

 

 ===

 

“Hold still,” Black snapped, dabbing ointment along the cuts inside Red’s femurs.  The unguent prickled over the damaged bone in a way that wasn't entirely unpleasant, but also wasn't especially comfortable.

“’S fine,” Red slurred, lifting his head off the pillow so he could grin weakly at the other skeleton.

“It is NOT fine,” Black growled, pressing a gauze pad over the cut and bandaging it gently with a roll of tape.  “With your slovenly habits, it has a high chance of these getting infected, so I will be doing this every day until I am satisfied you’ve healed.  No excuses.”

Red sighed contentedly, feeling warm and completely wrung out as Black began patting down his sacrum with a warm washcloth.  “It’ll be fine then, ‘cause you’re watching them,” Red mumbled, eyesockets drifting closed as his interdimensional double carefully cleaned and bandaged each cut.

“Yes it WILL, no thanks to you,” Black grumbled, then gave Red a light smack on the hip.  “No sleeping until you’ve finished your tea.”

Red grumbled under his breath, then clumsily pushed himself upright with a wince.  He knew that it was literally going to be a pain to sit for a week, but instead of dread, the thought was oddly thrilling.

“All of it,” Black prompted him, pushing the cup in his hands.

Red grimaced and took a sip.  His expression relaxed when he realized the brew was something herbal and minty, instead of Black’s usual, undrinkably strong Earl Grey.  It wasn’t nearly sweet enough, but hell, it was warm, he was thirsty, and Black was literally hand-feeding it to him.

“Thanks,” Red mumbled, finishing off the mug.  Black took it back and helped him lie down on his front to keep the pressure off his cuts.

“Your welcome,” Black grumbled, tucking a blanket carefully over his partner.  “Now get to sleep so you can get your buffer back.  I’m sure I took a good chunk out of it with the knife-play.”

“’kay,” Red mumbled, already half asleep.  Black rolled his eyes, then climbed into bed and gently transferred Red’s head into his lap.  Cuddling was out for the moment, since the other skeleton needed to sleep face-down to stay off his cuts, but the least Black could do was hang around until his partner woke up.  Just in case.

**Author's Note:**

> How long has it been since I did something entirely self-indulgent?? *whispers* too long...
> 
> Also wanted to point out that, in this case, the tea WAS aftercare for Red, but making it and giving it to him to drink was aftercare for Black. Doms need aftercare too, after all...


End file.
